Abstract

Surface plasmon polaritons (SPPs) Bragg reflector with more excellent optical properties are investigated numerically. By introducing a finite array of periodic grooves on the two surfaces of metal-insulator-metal (MIM) waveguide, we fulfill the periodical changes of effective refractive index, which leads to the photonic band gap (PBG). And it has been further widened by inserting a dielectric material with higher refractive index in the waveguide with narrow slit width. Finite difference time domain (FDTD) simulation confirms the widened bandgap. In addition, a SPP nanocavity is introduced by breaking the periodicity of our proposed structure.

Figures (4)

(Coloron line) (a) Scheme of two MIM waveguides with slit widths wA,wB, respectively, produced by engraving two grooves on the surfaces of a single MIM waveguide. Here, dA and dB designate the waveguide thicknesses and the red section is metal. (b)–(c)Schematic of plasmonic Bragg reflector, alternately filled with air/air and SiO2/air, respectively.

(Color on line) Variation of the real (a) and imaginary (b) parts of neff with wavelength for SPPs mode in the MIM waveguide. The two insets show the real and imaginary of neff as a function slit width. The thin solid, thin dash lines (red) and thick solid line (blue) correspond to the MIM waveguide with dielectric SiO2 (εd=1.46), PSiO2 (εd=1.23), air (εd=1.0), and the same slit width as Ref. 15, w=30nm. The thick dash-dot line presents MIM structure filled with air, w=100nm.

(Color on line)(a) Transmission spectrum of Bragg reflector consisting of 10 periods. The thin (black) line represent the MIM Bragg reflector with periodic changes of dielectric in the slit, width w=30nm. The thick red and blue solid lines stand for the structure shown in Fig. 1(b) and (c), respectively. The slit widths are wA=30nm,wB=100nm, respectively. (b) Bandgap as a function of slit width difference h=wB-wA, filled with dielectric in the narrow MIM waveguides (εd=2.5). The inset shows bandgap as a function of dielectric constants with h=70nm.(c)–(d) The field distribution of |Hz|2 in the reflector (Fig. 1(b)) at λ=1µm and λ=1.55µm, respectively. (e)–(f) |Hz|2 distribution for the cases shown in Fig. 1(b) and (c) at λ=1.3µm, respectively. The white thin lines give the profile of the reflector.

(Color on line)(a)Transmission of nanocavity with different dielectric/air alternately filled in the slits and grooves. The thick solid(blue), thin solid(black) and thick solid lines (red) correspond to the dielectric constants as εd=1.46,εd=1.23,εd=1.0, respectively. (b)–(c) The field distribution of |Hz|2 for defect mode at λ=1.55µm, filled with air/air, SiO2/air, respectively.